Bisphenol-A (BPA) is prepared by the reaction of phenol and acetone in the presence of an acidic catalyst, such as HCl or an ion exchange resin. During the reaction, a number of unwanted by-products and color are formed which affect yield and quality. The formation of such by-products and color is related to acetone concentration, retention time and temperature in the reactor. Some of the by-products are precursors of other impurities which can be formed in the various purification steps (distillations, crystallizations, etc.) used to produce the desired final product quality.
Typically, the BPA reaction is run in such a way that all the acetone in the reactor feed stream is consumed till depletion to achieve the desired capacity. This results in high retention times With the subsequent formation of extra by-products. It is desired to reduce the retention time, the resulting unwanted by-products and minimize the color effects.